Time-delay circuit for electric discharge devices

ABSTRACT

A time-delay circuit, preferably for use for delaying application of full voltage to an electric discharge device, including a pair of spaced terminals for connection to a voltage source, a relay including a coil and at least first and second normally open contacts with the relay coil and the first normally open contact being connected in series with the pair of spaced terminals, the second normally open contact when in closed condition connecting one of the aforesaid pair of spaced terminals in series with a third terminal, a thermal delay device including a current-responsive heater and a third normally open contact, the latter contact being closed in response to a predetermined period of current flow through the heater, the heater of the thermal delay device being connected in series with the aforesaid relay coil between the pair of spaced terminals, and the first and third normally open contacts being connected in parallel with the heater of the thermal delay device whereby closure of the third normally open contact in response to the predetermined period of current flow through the heater results in sufficient current flow through the relay coil to effect closure of the first and second normally open contacts, closure of the first normally open contact maintaining energization of the relay coil and effecting deenergization of the heater, and closure of the second normally open contact connecting the third terminal to one of the pair of spaced terminals resulting in full voltage being applied to the electric discharge device.

limited States Patent [72] Inventor Art Lee Bloomington, Ill. [21] Appl. No. 27,620 [22] Filed Apr. 13, 1970 {45] Patented Aug. 10, 1971 [73] Assignee General Electric Company [54] TIME-DELAY CIRCUIT FOR ELECTRIC DISCHARGE DEVICES 4 Claims, 2 Drawing Figs.

[52] U.S.CI 317/141, 315/100, 315/102, 315/104 [51] Int. Cl ..H01h47/l8 [50] FieldofSearch 317/141; 3l5/100,102, 104

[56] References Cited UNITED STATES PATENTS 2,497,542 2/1950 Frech 315/100 2,935,659 5/1960 Zangerle 3l5/100X Primary Examiner-J. D. Miller Assistant Examiner-Harry E. Moose, J r,

Att0rneys-Arthur E. Fourier, J12, David M. Schiller, Frank L.

Neuhauser, Oscar B. Waddell and Joseph B. Forman ABSTRACT: A time-delay circuit, preferably for use for delaying application of full voltage to an electric discharge device, including a pair of spaced terminals for connection to v a voltage source, a relay including a coil and at least first and second normally open contacts with the relay coil and the first normally open contact being connected in series with the pair of spaced terminals, the second normally open contact when in closed condition connecting one of the aforesaid pair of spaced terminals in series with a third terminal, a thermal delay device including a current-responsive heater and a third normally open contact, the latter contact being closed in response to a predetermined period of current flow through the heater, the heater of the thermal delay device being connected in series with the aforesaid relay coil between the pair of spaced terminals, and the first and third normally open contacts being connected in parallel with the heater of the thermal delay device whereby closure of the third normally open contact in response to the predetermined period of current flow through the heater results in sufficient current flow through the relay coil to effect closure of the first and second normally open contacts, closure of the first normally open contact maintaining energization of the relay coil and effecting deenergization of the heater, and closure of the second normally open contact connecting the third terminal to one of the pair of spaced terminals resulting in full voltage being applied to the electric discharge device.

PATENTEB AUG l men INVENTOR ART LEE BY gm 5* yaw.

ATTORNEY TIME-DELAY CIRCUIT FOR ELECTRIC DISCHARGE DEVICES BACKGROUND OF THE INVENTION 1. Field of the Invention My invention relates to time-delay circuits, and more particularly to a novel and improved thermal time-delay circuit primarily for use in effecting the delay application of full voltage to an electric discharge device such as a fluorescent tube.

2. Description of the Prior Art It has long been the accustomed practice for business interests be they commercial or industrial to advertise the location of their establishment through the means of some form of advertisement. One particular form of advertisement which has been utilized to advantage for this purpose is the large outdoor sign. Such signs when located at the site of the establishments serve to attract potential customers thereto. Further such signs have proven to be particularly effective when supported at heights suitably selected to be, visible to prospective customers from afar. Although these signs often include some means of drawing attention thereto in the daylight apart from their conspicuous location, such as for example means for causing the sign to rotate in the daytime, etc., such signs almost always are provided with some form of lighting means whereby the sign may be lighted for at least a portion of each night.

However, because of the extreme height at which many of these signs are located, the task of replacing the lighting elements thereof when the latter burn out has proven to be not only time consuming but also relatively expensive. On the other hand, unless the burned out lighting elements are replaced as the need arises, the advertising potential of the sign will of course be diminished if not lost. Thus, an attempt is generally made to keep the lighting elements of the sign functioning properly at all times notwithstanding the difficulties which this may involve. For example, in the case of those signs supported at considerable heights, the replacement of lighting elements therein may require the use of costly special equipment. That is, these signs often are too high up in the air to permit a workman to reach them by means of the conventional ladder. Thus, it has proven from an economic standpoint to be desirable to provide such signs with lighting elements which are characterized by their normally longer life notwithstanding the fact that such lightingelements may individually be somewhat more costly than other lighting elements having equivalent light potential but a shorter lifespan.

The savings to be derived from having to replace the lighting elements of the signs at less frequent intervals because of the longer life characteristics of the lighting elements more than makes up for any added cost which may be involved in utilizing lighting elements having such longer life characteristics.

One of the most commonly employed forms of lighting elements used in such signs is fluorescent tubes. One method of achieving longer life in lighting elements such as fluorescent tubes comprises preheating the filaments of the tubes before full voltage is applied thereto. Thus, it has been found that if the filaments of fluorescent tubes are preheated to establish an ion cloud around each filament prior'to the application of full operating voltage to the tube the are created at the time of application of full operating voltage will be absorbed by the aforementioned ion cloud around the filaments instead of by the cold filaments themselves thereby substantiallyreducing if not eliminating the occurrence of end blackening of the tubes, the latter being one of the primary factors influencing the life of fluorescent tubes. Tests have proven that by delaying the 1 application of full voltage to the fluorescent tubes by means of the special time-delay control circuit which is the subject of the present invention, thereby permitting preheating of the filaments to occur, the life of the fluorescent tubes tested has approximating 30,000 hours.

2 OBJECTS OF THE INVENTION It is therefore an object of the present invention to provide a novel and improved thermal time-delay circuit primarily for use in effecting the delayed application of full operating voltage to an electric discharge device such as a fluorescent tube.

It is another object of the present invention to provide such a thermal time-delay circuit which permits preheating of the tube to occur before full operating voltage is applied thereto thereby producing a significant increase in the normal lifespan of the tube.

A further object of the present invention is to provide such a thermal time-delay circuit wherein the increase in tube life produced by use of the subject circuit is of a sufficient magnitude to warrant the relatively small additional expenditure involved in providing the subject circuit.

Yet another object of the present invention is to provide sucha thermal time-delay circuit which is capable of being employed with present equipment without the need for substantial modification of the latter equipment.

Yet a further object of the present invention is to provide such a thermal time-delay circuit which is versatile in application, easy to use, reliable in operation, and relatively inexpensive to produce.

SUMMARY OF THE INVENTION In accordance with a preferred form of the invention there is provided a thermal time-delay circuit primarily for use in effecting the delayed application of full operating voltage to electric discharge devices such as fluorescent tubes. The subject circuit includes a pair of spaced terminals for connection to a voltage source, and a relay having a coil and at least first and second normally open coats. The coil of the relay and the first normally open contact are connected in series with the pair of spaced terminals. The second normally open contact of the relay when in a closed condition connects a third terminal in series with one of the pair of spaced terminals. In addition, the subject circuit includes a thermal delay device having a current-responsive heater and a third normally open contact which is closed in response to a predetermined period of current flow through the heater. The heater of the thermal delay device is connected with the coil of the relay in series with the pair of spaced terminals. The'first and third normally open contacts are each connected in parallel with the heater of the thermal delay device such that closure of the third normally open contact in response to the predetermined period of current flow through the heater results in sufficient current flow through the relay coil to effect closure of the first and second normally open contacts of the relay. Closure of the first normally open contact of the relay maintains energization of the relay coil and also effects deenergization of the heater. Closure of the second normally open contact of the relay connects the third terminal to one of the pair of spaced terminals allowing full operating voltage to be applied to the fluorescent tubes.

The invention will be more fully understood from the followingdetailed description and its scope will be pointed out in the appended claims.

BRIEF DESCRIPTION OF THE DRAWING FIG. I is a schematic wiring diagram of a single-pole version of a thermal time-delay circuit in accordance with the present invention illustrated connected in circuit with the components of a fluorescent tube circuit; and

FIG. 2 is a schematic wiring diagram of a multipole version of the thermal time-delay circuit of FIG. 1 in accordance with the present invention illustrated connected in circuit with the components of a fluorescent tube circuit.

DESCRIPTION OF A PREFERRED EMBODIMENT Referring to FIG. 1 of the drawing, the invention as illustrated therein comprises a single-pole version of a thermal time-delay circuit, generally designated by reference numeral 10. The thermal time-delay circuit is shown connected in circuit with the components of a fluorescent tube circuit, generally designated by reference numeral 11. For clarity of illustration and understanding, the components of the fluorescent tube circuit'll are generally depicted enclosed within the dotted line 12.

The thermal time-delay 10 includes a pair of spaced terminals 13 and 14 which are connected to conductors 15 and 16, respectively, the latter in turn being connected to terminals 17 and 18, respectively, for connection to a suitable voltage source. The thermal time-delay circuit 10 further includes a relay having a coil 19 and a pair of normally open contacts 20 and 21 which are closed in response to a predetermined magnitude of current flow through coil 19. One end of i the coil 19 is connected by conductor 22 to terminal 23 and from terminal 23 through conductor 24 to previously described terminal 13. The other end of the coil 19 is connected by conductor 22 to terminal 25 and from terminal 25 through conductor 26 to contact 20a of normally open relay contact 20. The other contact, i.e., contact 20b of normally open relaycontact 20 is connected by conductor 27 to terminal 28 and from terminal 28 through conductor 29 to previously described spaced terminal 14. Thus, it is seen that the coil 19 and normally open contact 20 of the aforedescribed relay are connected in series with the pair of spaced terminals 13 and 14.

Referring still to FIG. 1 of the drawing, normally open contact 21 of the aforedescribed relay has one contact, i.e., contact 21a, connected by conductor 30 to terminal 23, while its other contact, i,e., contact 21b, is connected to terminal 31 by means of conductor 32. Accordingly, it is thus seen that when normally open contact 21 is in the closed condition, terminal 31 is connected in series through conductor 32, conductor 30, terminal 23,.and conductor 24 to spaced terminal 13.

Continuing with a description of the thermal time-delay circuit 10 illustrated in FIG. 1 ofthe drawin'g,'the latter circuit 10 also includes a suitable thermal time-delay device 33. In accordance with the preferred embodiment of the invention, the thermal time-delay device 33 comprises a thermal delay relay tube known in the art as an Amperite tube. The thermal timedelay device 33 includes a current-responsive heater 34 and a normally open contact 35 which is'closed in response to a predetermined period of current flow through the heater 34. An attempt has been made to illustrate this latter relationship in FIG. 1 through the use of dotted line 36 which is shown interconnecting heater 34 and normally open relay contact 35. The heater 34 is connected across terminals 25 and 28 by means of conductor 37. Thus, the heater 34 is connected with the relay coil 19 in series with the pair of spaced terminals 13 and 14. In addition, it is seen from FIG. 1 of the drawing that the heater 34 is connected in parallel with normally open contact 20 of the aforedescribed relay and with its own contact As illustrated in FIG. 1 of the drawing, the thermal timedelay circuit 10 of the present invention is depicted connected in circuit with a fluorescent tube circuit 11. For purposes of description of the method of operation of the thermal timedelay. circuit 10, the fluorescent tube circuit 11 has been chosen for illustration. However, it is to be understood that the thermal time-delay circuit 10 in accordance with the present invention can be readily employed with other forms of fluorescent tube circuits as well as with other type of circuits not shown in the drawing.

Only a brief general description of the fluorescent tube circuit 11 will be set forth hereinafter inasmuch as such circuits are well known to those skilled in this art. Thus, as shown in FIG. 1 of the drawing, fluorescent tube circuit 11 includes a ballast 38 connected in circuit with a plurality of fluorescent tubes. For purposes of illustration, the ballast 38 has been depicted connected in circuit with three fluorescent tubes 39, 40, and 41, respectively. However, the number of fluorescent tubes may of course vary depending on the type of ballast 38 being employed in the circuit and/or the particular lighting needs to be met by the circuit 11. Incoming power is supplied to ballast 38 through conductors 42 and 43 which are connected to terminals 13 and 14, respectively. As was previously described hereinabove in connection with a description of the thermal time-delay circuit 10, the terminals 13 and 14, respectively, are connected through conductors l5 and 16 to terminals 17 and 18, respectively, for connection to a suitable voltage source. The ballast 38 in turn is connected by suitable conductors to fluorescent tubes 39, 40, and 41. In addition, to complete the circuit through the ballast 38 and florescent tubes 39, 40, and 41, conductor 44 as shown in FIG. 1 of the drawing connects fluorescent tube 39 to terminal 45 which in turn is connected through conductor16 to terminal 18, while conductor 46 as shown connects ballast 38 with terminal 31 which as was described previously is connected in series with terminal 13 and from terminal 13 through conductor 15 to terminal 17 when nonnally open contact 21 is in the closed condition.

A description of the method of operation of the thermal time-delay circuit 10 will now be set forth. With the relay contacts 20 and 21 and the contact 35 of the thermal time-delay device 33 in the normally opened condition, power is applied to thermal time-delay circuit 10 through terminals 17 and 18, conductors 15 and 16, and terminals 13 and 14. Current will thus flow through the aforedescribed relay coil 19 and heater 34 of the thermal time-delay device 33. However, the resistance values of the coil 19 and the heater 34 are such that the current flow through the relay coil 19 is not sufficient to pull in the coil 19. After a predetermined period of current flow through the heater 34, the heater 34 causes the'normally open contact 35 associated therewith in the thermal timedelay device 33 to close. The aforesaid predetermined period of current flow necessary to cause the normally open contact 35 to close of course depends on the characteristics of the heater of the particular thermal time-delay device 33 employed in the thermal time-delay circuit 10. In accordance with the preferred embodiment of the invention, the aforesaid predetermined period'of current flow is selected to be in the order of IO seconds. Now with the normally open contact 35 in the closed condition, the heater 34 is shunted thereby so that more current flows through the relay coil 19 which is sufficient to effect closure of the normally open contacts 20 and 21. This closing of the normally open contacts 20 and 21 when the relay coil 19 pulls in is representatively shown in FIG. 1 by means of dotted line 47 which as illustrated therein interconnects the normally open contacts 20 and 2]. Closure of normally open contact 20 maintains energization of the relay coil 19 and by permitting current flow through contact 21'in effect shorts out the heater 34 of thermal time-delay device 33. This permits the heater 34 to rapidly cool down whereupon normally open contact 35 which had been in the closed condition will return to its normally open condition. In accordance with the preferred embodiment of the invention, the heater 34 of the thermal time-delay device 33 is selected such that it will have the capability of cooling down sufficiently to permit normally open contact 35 to reopen approximately 1 minute after normally open contact 20 closes, and thus then be in condition for initiation of another cycle. Closure of normally open contact 21 connects-terminal 31 in series with spaced terminal 13 with the result that full operating voltage is applied through ballast 38 to the fluorescent tubes 39, 40, and 41 effecting full illumination of the latter tubes.

Following the application of power to thermal time-delay circuit 10 through the terminals 13 and 14 thereof, in the interval of approximately 10 seconds before the heater 34 causes the normally open contact 35 to close, sufficient power is applied through ballast 38 to fluorescent tubes 39, 40, and 41 to cause preheating of the filaments thereof. Such preheating effects the creation of an ion cloud around the filaments of the fluorescent tubes 39, 40, and 41 whereby when upon closure of normally open contact 21, full operating voltage is applied to the tubes 39, 40, and 41, the arc created thereby will be absorbed by the aforementioned ion cloud rather than the filaments themselves. This has the advantageous result of substantially prolonging the life span of the fluorescent tubes.

Referring now to FIG. 2 of the drawing, .there is illustrated therein a multipole version of the thermal time-delay circuit illustrated in FIG. 1. In accordance with the present invention such a multipole version is intended primarily for use in large signs which require a plurality of fluorescent tubes to illuminate them. Because only a predetermined maximum number of fluorescent tubes can be used with agivenballastjt oftenoccurs in large signs that a plurality of ballasts must be employed to service theplurality of fluorescent tubes required to adequately illuminate the sign. The thermal time-delayeirv cuit of ,-FIG.- 2 is capable of being employed in circuit with a plurality of ballasts, the latter each being in circuit with one or more fluorescent tubes. That is, the thermal time-delay circuit of-.FIG. 2, is capable ,of controlling a plurality of fluorescent tube circuitssirnilar. to the fluorescent tube circuit. 11 of FIG. 1. Ina'smuchasthe thermal time-delay circuit of FIG. 2 is substantially the same as the thermal time-delay circuit of FIG. 1, the components of the former thermal time-delay circuit which find correspondence in the circuitry of the thermal time-delay circuit of FIG. 1 are identified by the same reference numeral as usedin FIG. 1. but with the addition of a prime theretoQ Thus,whereas the thermaltime-delay circuit of FIG. 10 is designated by; referencehumeral '10, the thermal timeQdelay circuit of'FlGL-Z is designated'by reference numerall0". 4 c

The thermal time-delay circuit 10 of FIG. 2 includes a pair of spaced terminals 13 and 14' for connection to a voltage source and a relay having a coil 19' and four normally open contacts, i.e., contacts 20' and 21' which correspond to'normallyopen contacts 20 and 2l,-respectively, of thermal timedelay circuit 10 of FIG. 1, and contacts 48 and 49. The coil 19' of the relay and thenormally open contact 20' are connected inseries with the pair of spaced terminals 13' and '14. Normally open contact 21 when in a closed condition connects terminal 31' in series with spaced terminal 13' with the result that full operating voltage is applied through the ballast 38 to fluorescent tubes 39, circuit 11 effecting full illumination of, the latter tubes. Normally open contact 48 has one contact, i.e., contact 480, connected by conductor 50 to terminal 51,, while its other contact, i.e contact 48!), is connected to terminal 52 by means of conductor 53 thereby providing a series connection between terminal 52 and spaced terminal 13 when normally open contact 48 is in the closed condition. Thus, it is seen that normally open contact 48 functions like normally open contact 21' and that terminal 52 corresponds to terminal 31. That is, terminal 52 provides a connection to a ballast (not shown) of a second fluorescent tube circuit (not shown) similar to ballast 38' of fluorescent tube circuit 11'. Similarly, normally'open contact 49 has one contact, i.e., contact 49a, connected by conductor 54 to terminal 55 while its other contact, i.e., contact 49b, is connected to terminal 56 by means of conductor 57 thereby providing a series connection between terminal 56 and spaced terminal 13 when normally open contact 49 is in the closed condition. Thus, in the manner described hereinabove in connection with the description of normally open contact 48, terminal 56 provides a connection when normally open contact 49 isin the closed condition between the spaced terminal 13' an daballast (not shown) similar to the ballast38' of fluoresc e'nt tube circuitll'. i

In addition, thermal time-delay circuit 10 includes a thermal time-delay device 33 having a current responsive heater 34 and a normally open contact 35 which is closed in response to a predetermined period of current flow through the heater 34'. The heater 34' of the thermal time-delay device 33' is connected with the coil 19 of the relay in series with the pair of spaced terminals 13' and 14". The normally open contacts 20', 21, 48, and 49 are each'connectedin parallel with the heater 34 of the thermaltimesdelay device 33 such that closure of normally open contact35'- in response 'to the predeterminedperiod of current flow through the heater34' results in sufficient current flow through the relay coil 19 to effect closure of normally open contacts 20', 21', 48, and 49 of the relay. This closing of the normally open contacts 20, 21', 48, and 49 when the relay coil 19' pulls in is representatively shown in FIG. 2 by means of dotted line 58 which as illustrated therein interconnects the normally open contacts 20, 21, 48, and 49.,Closure of normally open contact 20"maintains energization of therela ycoil 19' and also effects deenergization of the heater 34 byshorting out thermal time-delay device 33 thereby permitting heater34' to 'coolldown sufficiently to cause normally open contact to return to its normally open state wherein it is in condition for initiation of another cycle of operation. Closure of normally open contact 21' connects terminal 31' to spaced terminal 13' allowing full operating voltage to be applied to the fluorescent tubes 39', and 41' of fluorescent tube circuit 11. Normally open contacts 48 and ,49 function in a similar manner. That is, closure of normally open contact 48 connects terminal 52 to spaced terminal 13' allowing full operating voltage to be applied to the fluorescent tubes of 'a second fluorescent tube circuit, and closure of normally open contact 49 connects terminal 56 to spaced terminal 13 allowing full operating voltage to be applied to the fluorescent tubes of a third fluorescent tube circuit. It is thus seen that by theaddition of two more normally open contacts to the relay of thermal timedelaycircuit 10', the latter is capableof controlling a second and a third fluorescent tube circuit similar tofluorescent tube circuit ll'LThe advantages resulting from the utilization of thermal time-delay circuit 10' with fluorescent tube circuit ll as set forth hereinabove in connection with the description of thermal time-delay circuit 10 of FIG. 1, are also derived in utilizing the thermal time-delay circuit 10' in connection with the aforesaid second and third fluorescent tube circuits. That is, it is to be understood that preheating of the filaments of the fluorescent tubes of the aforesaid second and third filament tube circuits would take place, in the intervalof approximately 10 seconds before the heater 34 causes the normallyopen contact 35 to close.

Two particular advantages to be noted which stem fromthe use of the thermal time-delay device 33 in series with the coil 19 are that the total time delay of -the thermal time-delay device 33 is not adversely affected by this circuit arrangement and that this circuitarrangement by permitting the utilization of a single normally open contact in parallel with the contact 35 of the thermal time-delay device 33 so that the power can easily be removed from the thermal time-delay device 33 allows the latter to cool down and have its contact 35 open so that it is ready for the next timing event without undue delay.

Thus, in accordance with the present invention there has been provided a novel and improved thermal time-delay circuit primarily for use in effecting the delay application of f ii! operating voltage to an electric discharge device such as a fluorescent tube. The subject circuit permits preheating of the tube to occur before full operating .voltage is applied thereto thereby producing a significant increase in the normal lifespan of the tube. Moreover, the increase in tube life produced by use of the subject circuit is of a sufficient magnitude to warrant the relatively small additional expenditure involved in providing the subject circuit. Also, the thermal time-delay circuit provided in accordance with the present invention is capable of being employed with present equipment without the need for substantial modification of the latter equipment. Finally the subject thermal time-delay circuit is characterized by its versatility of application, ease of use, reliability in operation, and relative inexpensiveness to produce.

tubes utilized in fluorescent tube circuits 11 and 11' need not necessarily number three. Moreover, the thermal time-delay circuit of FIG. 2 may include fewer or more normally open contacts than the four, i.e., contacts 20', 21, 48, and 49 depicted'in FIG. 2. l therefore intend by the appended claims to cover the above modifications as well as all other modificationswhich fall within the true spirit and scope of my invention. f

What lclaim as new and desire to secure by LettersPatent of the United States is: p

l. A time-delay circuit for delaying application of full operating voltage to at least one electric discharge device comprising:

a. a pair of spaced first terminals for connection to a voltage source;

b. a first relay including a coil and at least first and second normally open contact means which are closed in response to a predetermined magnitude of currentfiow through said coil; V

c. said coil and said first normally open contact means being connected in series between said pair of spaced first terminals;

d. a third terminal which when connnected to one of said pair of spaced first terminals results in application of full operating voltage to said discharge device;

c. said second normally open contact means being connected between said third terminal and said one of said pair of spaced terminals; v

. a thermal time-delay device including a current-responsive heater and a third normally open contact means which is closed in response to a predetermined period of current flow through said heater; 1

g. saidfheater and said coil being connected in series between said pair of spaced first terminals and having resistance values such that current flowing between said pairof spaced first terminals through said coil and said heater is less than said predetermined magnitude of current flow; and

h. said first and third normally open contact means each being connected in parallel with said heater, closure of said third normally open contact means in response to said predetermined period of current flow through said heater effecting said predetermined magnitude of current flow through said coil to close said first and second normally open contact means, closure of said first normally open contact means maintaining energization of said coil and effecting deenergization of said heater, and closure of said second normally open contact means connecting said third terminal to said one of said pair of spaced first terminals.

2. A time-delay circuit as set forth in claim 1 wherein: p

a. said time-delay circuit'additionally delays application of full operating voltage to at least a second and at least a third electric discharge device;

b. said first relay further includes at least another pair of normally open contact means which are each closed in response to said predetermined magnitude of current flow through said coil;

c. a fourth terminal which when connected to said one of said pair of spaced first terminals results in application of full operating voltage to at least said second electric discharge device; I

d. a fifth terminal which when connected to said-one of said pair of spaced first terminals results in application of full operating voltage to at least said third electric discharge device;

e. one of said another pair of normally open contact means being connected between said fourth terminal and said one of said pair of spaced first terminals;

f. the other of said another pair of normally open contact means being connected between said fifth'terminal and said one of said air of spaced first terminals; and g. closure of sat third normally open contact means in response to said predetermined period of current flow through said heater effects said predetermined magnitude of current flow through said coil to also close said another pair of normally open contact means, closure of said one of said another pair of normally open contact means connecting said fourth terminal to said one of said pair of spaced first terminals, and closure of said other of said another pair of normally open contact means connecting said fifth terminal to said one of said pair of spaced first terminals.

3. A time-delay circuit comprising:

a. a pair of spaced terminals for connection to a voltage source;

b. a first relay including a coil and at least first and second contact means which are operated in response to a predetermined magnitude of current flow through said coil, said first contact means being normally open and operated to closed condition;

c. said coil and said first contact means being connected in series between said pair of spaced terminals;

d. a thermal time-delay device including a current-responsive heater and a' third normally open contact means which is closed in response to a predetermined period of current flow through said heater;

e. said heater and said coil being connected in series between said pair of spaced terminals and having resistance values such that current flowing between said pair of spaced terminals through said coil and said heater is less than said predetermined magnitude of current flow; and

f. said first and third contact means each being connected in parallel with said heater, closure of said third contact means in response to said predetermined period of current flow through said heater effecting said predetermined magnitude of current flow through said coil to close said first contact means and to operate said second contact means, closure of said first contact means maintaining energization of said coil and effecting deenergization of said heater, and operation of said second contact means effecting a controlling function.

4. A time-delay circuit as set forth in claim 3 wherein:

a. said first relay further includes at least another contact means which is operated in response to said predetermined magnitude of current flow through said coil;

b. said thermal time-delay device comprises a thermal timedelay relay tube; and

c. closure of said third contact means in response to said predetermined period of current flow through said heater effects said predetermined magnitude of current flow through said coil to operate said another contact means. and operation of said another contact means effects a second controlling function. 

1. A time-delay circuit for delaying application of full operating voltage to at least one electric discharge device comprising: a. a pair of spaced first terminals for connection to a voltage source; b. a first relay including a coil and at least first and second normally open contact means which are closed in response to a predetermined magnitude of current flow through said coil; c. said coil and said first normally open contact means being connected in series between said pair of spaced first terminals; d. a third terminal which when connnected to one of said pair of spaced first terminals results in application of full operating voltage to said discharge device; e. said second normally open contact means being connected between said third terminal and said one of said pair of spaced terminals; f. a thermal time-delay device including a current-responsive heater and a third normally open contact means which is closed in response to a predetermined period of current flow through said heater; g. said heater and said coil being connected in series between said pair of spaced first terminals and having resistance values such that current flowing between said pair of spaced first terminals through said coil and said heater is less than said predetermined magnitude of current flow; and h. said first and third normally open contact means each being connected in parallel with said heater, closure of said third normally open contact means in response to said predetermined period of current flow through said heater effecting said predetermined magnitude of current flow through said coil to close said first and second normally open contact means, closure of said first normally open contact means maintaining energization of said coil and effecting deenergization of said heater, and closure of said second normally open contact means connecting said third terminal to said one of said pair of spaced first terminals.
 2. A time-delay circuit as set forth in claim 1 wherein: a. said time-delay circuit additionally delays application of full operating voltage to at least a second and at least a third electric discharge device; b. said first relay further includes at least another pair of normally open contact means which are each closed in response to said predetermined magnitude of current flow through said coil; c. a fourth terminal which when connected to said one of said pair of spaced first terminals results in application of full operating voltage to at least said second electric discharge device; d. a fifth terminal which when connected to said one of said pair of spaced first terminals results in application of full operating voltage to at least said third electric discharge device; e. one of said another pair of normally open contact means being connected between said fourth terminal and said one of said pair of spaced first terminals; f. the other of said another pair of normally open contact means being connected between said fifth terminal and said one of said pair of spaced first terminals; and g. closure of said third normally open contact means in response to said predetermined period of current flow through said heater effects said predetermined magnitude of current flow through said coil to also close said another pair of normally open contact means, closure of said one of said another pair of normally open contact means connecting said fourth terminal to said one of said pair of spaced first terminals, and closure of said other of said another pair of normally open contact means connecting said fifth terminal to said one of said pair of spaced first terminals.
 3. A time-delay circuit comprising: a. a pair of spaced terminals for connection to a voltage source; b. a first relay including a coil and at least first and second contact means which are operated in response to a predetermined magnitude of current flow through said coil, said first contact means being normally open and operated to closed condition; c. said coil and said first contact means being connected in series between said pair of spaced terminals; d. a thermal time-delay device including a current-responsive heater and a third normally open contact means which is closed in response to a predetermined period of current flow through said heater; e. said heater and said coil being connected in series between said pair of spaced terminals and having resistance values such that current flowing between said pair of spaced terminals through said coil and said heater is less than said predetermined magnitude of current flow; and f. said first and third contact means each being connected in parallel with said heater, closure of said third contact means in response to said predetermined period of current flow through said heater effecting said predetermined magnitude of current flow through said coil to close said first contact means and to operate said second contact means, closure of said first contact means maintaining energization of said coil and effecting deenergization of said heater, and operation of said second contact means effecting a controlling function.
 4. A time-delay circuit as set forth in claim 3 wherein: a. said first relay further includes at least another contact means which is operated in response to said predetermined magnitude of current flow through said coil; b. said thermal time-delay device comprises a thermal time-delay relay tube; and c. closure of said third contact means in response to said predetermined period of current flow through said heater effects said predetermined magnitude of current flow through said coil to operate said another contact means, and operation of said another contact means effects a second controlling function. 